The proposed research will investigate the cognitive and neurobiological processes underlying language comprehension and language learning. Event-related potentials (ERPs) will be recorded from numerous scalp locations while participants read sentences and discourses containing specific deviations from wellformedness. Prior work has shown that syntactic and semantic anomalies elicit distinct brain responses (the P600 and N400 effects, respectively). The proposed research has two goals. The first goal is to determine how a person coordinates his syntactic and semantic knowledge in deriving a single, coherent interpretation of a sentence. In particular, the proposed research will replicate and extend our recent finding (Kim &Osterhout, in press) that a "semantic attraction" between a verb and a noun can determine how words in a sentence are combined, even when the attraction directly conflicts with unambiguous syntactic cues. The proposed research will investigate the robustness of this effect and the variables that produce or modulate it, thereby delineating factors that determine whether syntax or semantics is "in control" of sentence comprehension. The second goal is to investigate the acquisition of morphosyntax by adult secondlanguage learners, and more specifically the incorporation of this acquired knowledge into the on-line language comprehension system. We will examine the influence of two variables that are likely to have profound influences on second-language learning: L1-L2 similarity, and phonological realization of grammatical morphemes. We will also examine claims that grammatical learning involves discontinuous development, that is, qualitatively distinct stages. By furthering our knowledge of the neurocognitive bases of normal comprehension and language learning, the studies proposed here provide a critical basis for subsequent ERP investigations of language pathologies and normal and abnormal language learning.